José Ribamar Smolka Ramos
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ComUnidade WirelessBrasil

Julho 2006               Índice Geral


IPv6, multihomed hosts e possibilidades...

----- Original Message -----

Sent: Wednesday, July 19, 2006 9:02 AM
Subject: [] IPv6, multihomed hosts e possibilidades...

Falando em IPv6... Estava "xeretando" o que anda acontecendo com os working groups do IETF ( que estão tratando de mobilidade com IPv6, e encontrei um grupo interessante, chamado monami6 (Mobile Nodes and Multiple Interfaces in IPv6). A página do grupo no site do IETF é, e eles mantém uma página adicional em

O assunto é novo (o grupo só foi estabelecido em outubro do ano passado), mas já desenha algumas coisas muito interessantes. Em particular, vou transcrever para vcs os cenários descritos em um dos documentos draft do grupo (Motivations and Scenarios for Using Multiple Interfaces and Global Addresses em

Boa leitura... Em outro post farei comentários adicionais.

Mona is just getting out of a meeting with customers in a building. She calls her head office. This audio communication is initiated via a private wireless local area network (WLAN) link realized over one of the available WI-FI hot-spots in the building. This is going to be a long call and she must attend another meeting a few minutes drive from here. She walks to a taxi stand, and boards a taxi. The audio communication is automatically transferred to the public wireless metropolitan area network (WMAN) over the WIMAX network deployed in the city, with no interruption of the communication.

Oliver is on his way to work waiting at a train station. He uses this opportunity and the presence of a WLAN hot-spot to download the news from his favorite on-line news channel. While Oliver is downloading the news, he receives a phone call over a wide area cellular link. Oliver decides he wishes to initiate a video flow for this communication. The bandwidth and traversal delay of the wide area cellular link is not adequate for the video conference, so both flows (video/audio) are transferred to the WLAN link provided by the hot-spot. This transfer occurs transparently and without affecting the other active flows.

Nami works at home for a publishing company. She has an in-house network and get access to the Internet via ADSL, a public 802.11b WLAN from the street and satellite. She has subscribed to the cheapest ADSL service with limited uplink bandwidth. Also, the satellite link she has access to is downlink only, but it is extremely cheap for TV broadcasting. She has noticed the 802.11b link is unreliable at some point in time during the day, so she chooses to send requests and periodic refreshments for joining the TV broadcasting via ADSL rather than 802.11b although it is free. On the other hand, she has configured her network to use the 802.11b link at night to publish web content comprising video. Once a week, she communicates with overseas peer staff by videoconferencing. Voice being the most important, she has configured her VoIP session over ADSL. Video is sent at maximum rate when 802.11b is working fine, otherwise the video is sent at lower rate.

Alice is a paramedic. Her ambulance is called at the scene of a car accident. She initiates a communication to a hospital via a wide area cellular link for the relay of low bit-rate live video from the site of the crash to assess the severity of the accident. It is identified that one of the passengers has suffered a severe head injury. The paramedic decides to consult a specialist via video conferencing. This session is initiated from the specialist via the same wide area cellular link. Meanwhile, the paramedic requests for the download of the patient medical records from the hospital servers. The paramedic decides in mid-session that the wide area cellular link is too slow for this download and transfers the download to the ambulance satellite link. Even though this link provides a significantly faster bit rate it has a longer traversal delay and only down-link is available. For this, only the downstream of the download is transferred while upstream proceeds over the wide area cellular link. Connectivity with the ambulance is managed over a WLAN link between the paramedic and the ambulance. Even though the paramedic has performed a partial hand-off for the transfer of the download down-stream to the satellite link, the upstream and the video conferencing session remains on the wide area cellular link. This serves best the time constraint requirements of the real time communications.

Max drives his car and constantly keeps some sort of Internet connectivity through one of the available access technologies. His car navigator downloads road information from the Internet and his car-audio plays on-line audio streaming. When his car passes an area where both high-data-rate WLAN and low-data rate cellular network are available, it distributes load to the WLAN access and the cellular network access. When his car passes an area where only a wide coverage-range cellular network is available, the connection is maintained via the cellular network.

Dr. Ingrid performs an operation via long-distance medical system. She watches a patient in a battlefield over the screen which delivers real-time images of the patient. Sensors on her arms deliver her operational actions and a robot performs the actual operation in the battlefield. Since the operation is critical, the delivery of patient images and Dr. Ingrid's action is done by bi-casting from/to multiple interfaces bound to a distinct technology or distinct radio range. So in case packets are delayed or one of the interfaces fails to maintain connectivity to the network, her distant operation can be continued.

Roku is at the airport waiting to board the plane.  She receives a call from her husband. This audio communication is received via a wireless local area network (WLAN) link realized over one of the available hot-spots. She knows this is going to be a long flight and wishes to catch up on some work. Roku uses a WLAN connection to download the necessary data. However, there is not enough time and she decides to accelerate the download. Her notebook is equipped with an additional WLAN interface. She decides to use this additional WLAN interface to connect to another access point, and distribute the different download flows between the two wireless interfaces.

[ ]'s

J. R. Smolka


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